1. Field of the Invention
The present invention relates to a digital video signal recording/reproducing apparatus for recording a digital video signal to a record medium and reproducing a digital video signal from a record medium, and a method thereof.
2. Description of the Related Art
A signal processing apparatus that digitally processes a video signal (for example, a signal processing apparatus for use with a digital VTR (Video Tape Recorder) that records/reproduces a high resolution video signal) performs a picture compressing and encoding process for an input picture signal. The compressed and encoded video signal is recorded to for example a video tape.
As compressing and decoding methods for interlaced video signals, an intra-frame encoding process and an intra-field encoding process are known. The compression efficiency of the intra-field encoding process is generally inferior to the compression efficiency of the intra-frame encoding process. Since the information amount of a high resolution video signal is around five times larger than the information amount of a standard resolution video signal, the intra-frame compressing process should be used.
In a digital VTR, pictures can be edited in individual frames. However, pictures based on a movie film may be edited. Thus, the necessity for editing pictures in individual fields is high. For example, when a movie material with a format of 25 frames/sec is converted into a video signal with a format of 30 frames/sec, a scene change may take place in two fields of the same frame. In this case, a picture should be edited in each field.
In addition to an editing method using two VTRs (a recording VTR and a reproducing VTR), another editing method using one VTR is often used. In the latter method, a picture reproduced from a tape and a picture to be input to the VTR are edited. The edited picture is recorded. The editing method for editing pictures in individual fields with one VTR is referred to as field editing method.
When the field editing method is performed in the intra-frame compressing and encoding process (namely, a picture should be edited at the end of a field), a frame may contain pictures that scarcely correlate with each other in the fields, for example. Namely, when the intra-frame compressing and encoding process is performed, the compressing efficiency may not be improved. In addition, since a picture is compressed in each frame, an output signal of the error correction decoder cannot be edited in each field.
Therefore, an object of the present invention is to provide a digital video signal recording/reproducing apparatus that allows pictures to be edited in individual fields and that prevents the compressing efficiency from being deteriorated.
The present invention is a digital video signal recording/reproducing apparatus for recording a digital video signal to a record medium and reproducing a digital video signal from a record medium, comprising:
a first encoder for performing a compressing process for an input digital video signal;
a second encoder for performing an error correction code encoding process for a compressed signal received from said first encoder;
recording means for recording an output signal of said second encoder to a record medium;
reproducing means for reproducing a signal from a record medium;
a second decoder for performing an error correction code decoding process for a signal received from said reproducing means;
a first decoder for performing a decompressing process for an output signal of said second decoder; and
switching means, disposed in the preceding stage of said first encoder, for switching between a reproduced digital video signal that has been decompressed by said first decoder and the input digital video signal at the end of each field.
The present invention is a digital video signal recording/reproducing method for recording a digital video signal to a record medium and reproducing a digital video signal from a record medium, comprising the steps of:
compressing an input digital video signal;
encoding the compressed signal with an error correction code;
recording the signal that has been encoded with the error correction code to a record medium;
reproducing a signal from a record medium;
decoding the reproduced signal that has been encoded with the error correction code;
decompressing the decoded signal; and
switching between a reproduced digital video signal that has been decompressed and the input digital video signal at the end of each field.
In the digital VTR, decompressed video data is sent back to a switching means of the recording system. The switching means switches between reproduced data and input data at the end of each field. Thus, a field editing process can be accomplished for a digital VTR. In the compressing and encoding process, the intra-field encoding process or the intra-frame encoding process can be selected. When information that represents the selected encoding process is recorded, even if a picture largely varies at the end of a field, the compressing efficiency can be prevented from being deteriorated.
The above, and other, objects, features and advantage of the present invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.